I am taking about the square box BELOW where I am currently typing - do I have to provide a screen shot ? as per this list of what I see on screen:

You can't use one without the other. Hover your mouse over the reply button in the attachment and read what it says. If not for the button Alex pointed out the box you want checked would have to read your mind. Of course as Adoby pointed out if there is only one post in the thread then you can use it the way you describe, because there is only one post to use as a reply quote.

i would expect it to default to refering to the most recent message. Maybe things would be clearer if it were not there at all as I seemt o be the only person who
a) has any desire to use it ( you guys all use the other methods)
b) am the only guy who has trouble with it

enough for now though. I get what some of you are all saying.- that if I arrive back at ths thread, start typing in the quick replay box without clicking any other boxes, then it is only tickable on single message threads

i cannot tick the "quote message in reply" box ,either before or after typing in some quick reply text in the message box

so one of the above theories of how that tick box works /why that tick box exists Bites the dust ?

I agree, the quick reply box has a quote button but it does not work. This forum is heavily modified customized code that will be replaced in the near future. I doubt if there is a compelling reason to fix this.